The Moon has some impressive companions this weekend — a brilliant planet, a bright star, and a famous star cluster. The whole party is in good view by about one o’clock in the morning.

Tonight, the member of the party that’s closest to the Moon is the Pleiades star cluster, a little above or to the upper left of the Moon as they rise. Its brightest stars form the outline of a tiny dipper.

The Pleiades is more than 400 light-years away. Yet for centuries, the cluster has provided weather forecasts right here on Earth.

In ancient Greece, for example, sailors often studied the Pleiades before heading out to sea. If the cluster looked bright and clear, it was a harbinger of good weather. If it was obscured by high, thin clouds, then it was a sign of stormy weather — and a good time to stay home.

Villagers in the Andes Mountains of South America used the Pleiades to decide when to plant crops. Good visibility at the start of the planting season meant early and abundant rains, so villagers planted early; poor visibility meant poor rains, so planting started later. Recent studies have shown that the Pleiades was especially good at forecasting El Niño, which had a big impact on the rains.

The Moon’s other prominent companions are the star Aldebaran, which is below the Moon, and the dazzling planet Jupiter, farther to the Moon’s lower left. The Moon will snuggle even closer to them tomorrow night; more about that on our next program.